I want to know if there is a way that I can visualize the trajectory of a link like shown in gazebo8 plot3Dplugin.This is a new feature in gazebo8, but I assume NRP is using gazebo7. Is there other alternative solution to achieve this functionality?

I know I can try to just grab this single plugin but when I check its source codes, it seems there are quite a lot changes Change Log here.

Hello, Zhenshan!Regarding your question about the plot3D plugin:- Using it in combination with the Gazebo version in the NRP will most likely not work out of the box. You assumed correctly that the NRP is currently using Gazebo 7.x. While most changes in the API between major releases of Gazebo are usually small, there is no certain way to guarantee downward compatibility for Gazebo plugins.- Another problem with the NRP is that there is currently no support to transfer trajectory data for visualization in the web frontend, both for Gazebo's web frontend (gzweb) and the NRP's own web frontend.

To add support for the plugin in the NRP, these two points would have to be addressed. From personal experience, adapting Gazebo plugins to a Gazebo version that is still somewhat "close" to the plugin's intended version is not too difficult. The same would be true for adding support for visualizing robot trajectory data in the web frontend of the NRP: The underlying visualization would support spline primitives, this would "just" be a matter of adding a new message type for sending the trajectory data to visualize from the Gazebo backend simulation to the web frontend.